Fullerene, carbon nanotube, graphene, graphite, and the like are low-dimensional nano-materials composed of carbon atoms. That is, carbon atoms arranged in a hexagonal shape may form a ball shape to be a zero-dimensional fullerene, may be one-dimensionally rolled, to be a carbon nanotube, may form two-dimensional monolayer to be graphene, and may be three-dimensionally stacked to be graphite.
In particular, graphene has very stable and excellent electrical, mechanical, and chemical characteristics and is a very excellent conductive material in which electrons can move about 100 times faster than in silicon and current flows about 100 times more than in copper. This has been demonstrated through experiments in 2004 when a method of separating graphene from graphite was found. Since then, a great deal of research on this matter has been carried out.
Graphene is made of pure carbons which are relatively light atoms, and, thus, it is very easy to process graphene in a one-dimensional or two-dimensional nano pattern. With this feature, it is possible to control semiconductive and conductive properties and also possible to manufacture various functional devices including sensors and memories using various chemical bonds of carbon.
Despite excellent electrical, mechanical, and chemical characteristics of graphene described above, a research of an applicable technology has been limited since a mass production method of graphene has not been developed. In a conventional mass production method, graphite is mechanically ground and dispersed in a solution to form a thin film via a self-assembly phenomenon. Although graphene can be produced at a relatively low cost by the conventional method, electrical and mechanical characteristics cannot meet the expectations due to a graphene structure in which numerous graphene pieces are overlapped and connected with each other.
Due to a recent surge in demand for flat panel displays, a global transparent electrode market is expected to grow to about twenty trillion won within about 10 years. With development of a display industry in Korea, a domestic demand for transparent electrodes reaches hundreds of billions of wons every year. However, due to a lack of original technologies, Korea heavily depends on imports for transparent electrodes. An ITO (Indium Tin Oxide) as a representative transparent electrode is widely applied to a display, a touch screen, a solar cell, and the like. However, recently, a lack of indium has contributed to an increase in cost, and, thus, there has been an urgent need to develop a substitute substance. Further, due to fragility of the ITO, there has been a limit in applications of the ITO to next-generation electronic devices which is foldable, bendable, and extendable. Graphene has been expected to have excellent elasticity, flexibility, and transparency and also expected to be produced and patterned by a relatively simple method. It is anticipated that a graphene electrode has a great import substitution effect if a mass production technology thereof can be established hereafter and also has an innovative ripple effect on the whole technologies in a next-generation flexible electronic industry.
However, if a substrate including graphene thereon is manufactured by such a method, it is not easy to place the graphene at a desired position on the substrate for manufacturing a device, and if graphene is formed on a substrate for manufacturing a device, it is necessary to use a resist and to perform a lift-off process. Thus, a patterning process becomes complicated and uneconomical (see Korean Patent Laid-open Publication No. 10-2011-0054386).